A large-sized dump truck operated in a mine, for example, for a haulage vehicle is provided with an operator cab in a position on the front side of a vehicle frame equipped with wheels and is provided with a vessel (body) for loading ore, rock, earth and others on the rear side of the operator cab. The vessel is coupled by hinge pins in a position on the rear side of the vehicle frame. Besides, a hoist cylinder is provided between the vehicle frame and the vessel and the vessel is tilted by driving the hoist cylinder.
After the dump truck loads a load such as earth onto the vessel in a loading location, it travels to a dumping location and dumps the load. An operator operates a control lever in the operator cab and tilts the vessel so as to dump the load (refer to a patent literature 1). The control lever can be tilted to a pushing-up position for pushing up the vessel, to a holding position for holding a tilted state of the vessel, to a floating position for pushing down the vessel with self-weight and to a pulling-down position for forcedly pulling down the vessel.
The operator tilts the control lever to the pushing-up position so as to push up the vessel up to an optimum angle to dump earth as a load from the vessel. Afterward, the operator tilts the control lever to the holding position so as to hold the vessel in that angular position by predetermined time. When dumping work is completed, the operator tilts the control lever to the floating position (or tilts it to the pulling-down position) so as to seat the vessel on the vehicle frame.
Besides, as disclosed in a patent literature 2 for example, technique for automatically controlling pushing-up operation and pulling-down operation of a vessel for dumping work is known. This patent literature 2 is the technique that when set time elapses, the vessel is pulled down.